Biological aging along with the subsequent process of cellular degradation of senescence clearly constitute universally occurring phenomena. At the present time aging is thought to consist of a complex series of events brought about by any number of possible cellular or molecular mechanisms. The overall objective of the present investigation will be to further expand our knowledge of the mechanism(s) responsible for the aging process. We hope to accomplish this goal by the following procedures: 1) The multicellular eucaryotic Volvox will be characterized as a model system for the study of biological aging and senescence. This organism appears to possess both the simplicity and ease of laboratory manipulation characteristic of unicellular microorganisms and yet is also capable of undergoing aging and senescence; processes generally only associated with more complex multicellular organisms. Because of these unique attributes, we believe the introduction of this organism as a model system for the study of aging and related phenomena will greatly benefit this field of research. 2) The role of mitochondria during the aging process in Volvox will also be examined in considerable detail. According to a widely accepted theory of aging, lipid peroxidation is thought to represent an important mechanism of cellular degeneration. Since mitochondria are considered to be primary targets of lipid peroxidation, a structural and functional examination of this organelle during the aging process should allow the evaluation of this theory. Possible alternative roles of mitochondria in the aging process also should be elucidated by this type of analysis.